The NOAA Coral Reef Watch (CRW) satellite Coral Bleaching Alert Area is part of the CRW operational near-real-time global 50-km satellite coral bleaching thermal stress monitoring product suite. This product suite was initially implemented in 2000 and continues to provide updated monitoring information twice-weekly. The Bleaching Alert Area product was added to the suite in 2009. This metadata file provides information on the Bleaching Alert Area product for both the most recent near-real-time updates and the archived product dating back to 2009. The satellite Bleaching Alert Area product identifies, for the twice-weekly time period ending on the day indicated in the product, locations where thermal stress reaches various levels that can lead to coral bleaching. A scale of five coral bleaching thermal stress levels, including No Stress, Bleaching Watch, Bleaching Warning, and Bleaching Alert Levels 1 and 2, is used. The thermal stress classification is described in detail at: <http://coralreefwatch.noaa.gov/satellite/baa.php>. Both the Bleaching Alert Area, as well as the level of stress defined by the product, are derived from Coral Bleaching HotSpots and Degree Heating Weeks (DHW) values measured at each site for any given twice-weekly time period. The DHW product (a key tool in the CRW operational product suite) measures accumulation of bleaching thermal stress that coral reefs experience over a period of 12 consecutive weeks (about 3 months), ending on the day indicated in the DHW product. The DHW product is derived from CRW's Coral Bleaching HotSpots product (another central tool in the operational product suite). A Coral Bleaching HotSpot is a specific type of sea surface temperature (SST) anomaly that measures the amount of SST exceeding a static coral bleaching threshold SST; it serves as a measure of instantaneous bleaching thermal stress and shows the occurrence, magnitude, and spatial distribution of the stress. All non-positive HotSpot values are recorded as zeros. The DHW value (again, a measurement of accumulated thermal stress) is, in its most simplistic form, the sum of all of the individual twice-weekly HotSpot values at any particular location within a 12-week period and with a magnitude of at least 1 degree Celsius, multiplied by the duration of the twice-weekly HotSpot value (i.e., 0.5 weeks). A more complicated formula describing how the DHW value is calculated can be obtained at: <http://coralreefwatch.noaa.gov/satellite/methodology/methodology.php#dhw>. One DHW is equivalent to one week of SST at 1 degree Celsius above the threshold, or 0.5 weeks of SST at two degrees Celsius above the threshold. Near-real-time satellite data from the Advanced Very High Resolution Radiometer (AVHRR) on some of NOAA's Polar Orbiting Environmental Satellites (POES) were used to generate AVHRR-SST that this CRW product suite is based on. The Bleaching Alert Area product is available in various formats, including static image, text, and Google Earth, and is delivered mainly through CRW's web site. The product, its detailed description, and available data formats and delivery mechanisms are accessible at: <http://coralreefwatch.noaa.gov/satellite>, along with general CRW product information and access to other CRW products.

Purpose:

The NOAA Coral Reef Watch program seeks to fully utilize space-based sea surface temperature (SST) observations combined with in-situ data to continually monitor for early indications of thermally-induced coral reef bleaching worldwide. A suite of monitoring and predicting products, including this satellite Bleaching Alert Area product, has been developed by CRW as a decision support system to provide critical and timely coral reef environment information to the U.S. and international coral reef communities.

This is the most recent image of NOAA CRW near-real-time twice-weekly global 50-km satellite Coral Bleaching Alert Area product.

Browse_Graphic_File_Type: GIF

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

The accuracy of the Bleaching Alert Area product depends on the accuracy of CRW's Degree Heating Weeks (DHW) and Coral Bleaching HotSpots products, which, in turn, depend on the accuracy of satellite SSTs and bleaching threshold SSTs. A full evaluation and validation of CRW HotSpots, DHWs, and the classification of the five bleaching thermal stress levels have not been completed yet. A preliminary evaluation revealed, however, that these products demonstrate remarkable success in detecting, monitoring, and predicting all large spatial scale mass coral bleaching events. Polar Orbiting Environmental Satellite (POES) AVHRR-SST values used for creating CRW 50-km SST analysis fields were accurate to within 0.5 degree Celsius and adjusted by in-situ buoy observations to best-approximate SST at the depth of one meter. However, when producing a complete, gap-filled SST analysis with global coverage, estimation of SST at the pixels covered by cloud may occasionally reduce the accuracy of SST at these pixels.

Logical_Consistency_Report: none

Completeness_Report:

There is no spatial data gap existing in this data set. No change will be made to the original Bleaching Alert Area data, but occasional revisions to some images may occur if an inaccuracy is detected in the image display of the data. New near-real-time Bleaching Alert Area products will be added continuously to this data at scheduled update times. The Bleaching Alert Area product has not been produced retrospectively back to 2000 to match the full time series of HotSpots and Degree Heating Weeks products In addition, animation and HDF data formats have not been implemented yet for the Bleaching Alert Area product. Retrospectively processed data and new data formats will be available soon on the CRW web site.

The Degree Heating Weeks and HotSpots products were derived from this SST product.

Process_Step:

Process_Description:

The level of coral bleaching thermal stress at a data grid presented in the Bleaching Alert Area product is determined by the values of Degree Heating Weeks and HotSpots at the data grid. A Degree Heating Week is calculated as the accumulation of Coral Bleaching HotSpots over 12 consecutive weeks. At each pixel, a coral bleaching threshold SST value is subtracted from the SST value to produce the Coral Bleaching HotSpot. See CRW web site at: <http://coralreefwatch.noaa.gov/satellite/index.php> and suggested references listed above for details.

There are 720 grid intersections in each row (at a pre-defined latitude) and 331 grid intersections in each column (at a pre-defined longitude). Each grid is 0.5 degree latitude by 0.5 degree longitude in size, centered at latitudes of from 80.0S northward to 85.0N and at longitudes of from 180W eastward to 179.5E.

NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.